Summary: Organic chemistry
The text in blue is info that will not be asked on the exam
Intro
Organic chemistry = chemistry of carbon-containing compounds
Why C?
1. Stable bonds with itself and quasy each other element
2. 4 stable covalent bonds
3. Single, double and triple bonds
Problems with adjacent elements:
B 3 bonds → very reactive
S Much bigger, no stable multiple bonds,…
i
N Free electron pair, no stable bbonds with itself
Components:
- bends are C’s
- H’s are omitted
- Functional groups with heteroatoms
H1&2: Basic concepts
Quantum numbers:
n Principal n = 1,2,3,…
l Azimuthal l = n-1
me Magnetic Between +l en -l
ms Spin +½, -½
3 rules occupation atomic orbitals (AO):
1. Low-energy AO’s are first filled
2. Pauli exclusion principle: 2 electrons can’t have 4 the same quantum numbers
3. Hund’s rule: largest number of unpaired electrons = favourable
Hybridisation
= Mixing of AO’s → new “hybrid orbitals”
C: hybrid orbital (spx):
p-orbital:
sp 3
Tetrahedral (109° 28’) 4 hybrids
sp2 Trigonal planar (120°) 3 hybrids
sp Linear (180°) 2 hybrids
1
,Summary
Bondings
Molecular orbital = linear combination of AOs or hybrid orbitals of different atoms
Bonding orbital (occupied with electrons, σ) + anti-bonding orbital (empty, σ*)
π-bond Multiple bond
Between 2 p-orbitals Shorter
Weaker Stronger
No free rotation No free rotation
Bond length → no linear relationship between single, double and triple bonds
Bond dissociation energy (= the energy needed to break the bond) → same
Elektronegativity
EN = the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself
EN of important atoms:
H 2,20 (≈C) S 2,58 (≈C) O 3,44
C 2,55 N 3,04 F 3,98
C-C and C-H-bonds: non-polar, very strong (backbones organic compounds), rather unreactive
Polarised bonds:
Atom Name In picture above Attracted to
Electron-poor Electrophiles C Nucleophiles
Electron-rich Nucleophiles X Electrophiles
Compound classes and functional groups
Hydrocarbon = only C and H
Aliphatic hydrocarbons Acyclic hydrocarbons Saturated Alkanes (C-C)
Linear, branched Unsaturated Alkenes (C=C)
Unsaturated Alkynes (C≡C)
Cyclic hydrocarbons Saturated Cycloalkanes (C-C)
2
, Containing rings Unsaturated Cycloalkenes (C=C)
Unsaturated Cycloalkynes (C≡C)
Aromatic hydrocarbons
Benzene and related compounds
Hydrocarbon derivates With halogens Haloalkanes R-F, R-Cl, R-Br, R-I
H3.1: Linear alkanes
General molecular formula: CnH2n+2
Type of molecules: acyclic, saturated, hydrocarbon, linear or branched
Hybridisation & bounds C atoms: sp3-hybridised, 4 covalent bounds
Formal oxidation state of C atoms: -4 to 0
Isomerism
= Molecules with the same kinds and numbers of atoms (same molecular formula) joined up in different ways.
Isomers Constitutional isomers
Stereoisomers Conformational isomers
Configurational isomers Enantiomers
Diastereomers
Explanation of concepts:
Concept Explanation Example
Constitutional isomers Same molecular formula but different connectivity
Stereoisomers Same molecular formula and connectivity, but
different spatial arrangement of atoms
Conformational isomers Can be interconverted by rotation around a bond -Staggered, eclipsed, …
(only σ-bond) -Chair conformations
Configurational isomers Can’t be interconverted by rotation around a bond -(E) and (Z) (around π-bond)
-Cis and trans decalin
-Chiral centres
Enantiomers Image and mirror image -Chiral centres
Diastereomers Not mirror images of each other. This occurs in -(E) and (Z) (around π-bond)
molecules with 2 or more stereo centres, where -Cis and trans decalin
the configuration is different at some but not all of -Multiple chiral centres, not
them. mirror images of each other
Constitutional isomers of alkanes:
Propanes
Butanes
Pentanes
Hexanes
Constitutional isomerism
Different chemical & physical properties
- Boiling point: linear alkanes are higher than branched alkanes
- Linear alkanes are thermodynamically less stable than branched alkanes
3
The text in blue is info that will not be asked on the exam
Intro
Organic chemistry = chemistry of carbon-containing compounds
Why C?
1. Stable bonds with itself and quasy each other element
2. 4 stable covalent bonds
3. Single, double and triple bonds
Problems with adjacent elements:
B 3 bonds → very reactive
S Much bigger, no stable multiple bonds,…
i
N Free electron pair, no stable bbonds with itself
Components:
- bends are C’s
- H’s are omitted
- Functional groups with heteroatoms
H1&2: Basic concepts
Quantum numbers:
n Principal n = 1,2,3,…
l Azimuthal l = n-1
me Magnetic Between +l en -l
ms Spin +½, -½
3 rules occupation atomic orbitals (AO):
1. Low-energy AO’s are first filled
2. Pauli exclusion principle: 2 electrons can’t have 4 the same quantum numbers
3. Hund’s rule: largest number of unpaired electrons = favourable
Hybridisation
= Mixing of AO’s → new “hybrid orbitals”
C: hybrid orbital (spx):
p-orbital:
sp 3
Tetrahedral (109° 28’) 4 hybrids
sp2 Trigonal planar (120°) 3 hybrids
sp Linear (180°) 2 hybrids
1
,Summary
Bondings
Molecular orbital = linear combination of AOs or hybrid orbitals of different atoms
Bonding orbital (occupied with electrons, σ) + anti-bonding orbital (empty, σ*)
π-bond Multiple bond
Between 2 p-orbitals Shorter
Weaker Stronger
No free rotation No free rotation
Bond length → no linear relationship between single, double and triple bonds
Bond dissociation energy (= the energy needed to break the bond) → same
Elektronegativity
EN = the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself
EN of important atoms:
H 2,20 (≈C) S 2,58 (≈C) O 3,44
C 2,55 N 3,04 F 3,98
C-C and C-H-bonds: non-polar, very strong (backbones organic compounds), rather unreactive
Polarised bonds:
Atom Name In picture above Attracted to
Electron-poor Electrophiles C Nucleophiles
Electron-rich Nucleophiles X Electrophiles
Compound classes and functional groups
Hydrocarbon = only C and H
Aliphatic hydrocarbons Acyclic hydrocarbons Saturated Alkanes (C-C)
Linear, branched Unsaturated Alkenes (C=C)
Unsaturated Alkynes (C≡C)
Cyclic hydrocarbons Saturated Cycloalkanes (C-C)
2
, Containing rings Unsaturated Cycloalkenes (C=C)
Unsaturated Cycloalkynes (C≡C)
Aromatic hydrocarbons
Benzene and related compounds
Hydrocarbon derivates With halogens Haloalkanes R-F, R-Cl, R-Br, R-I
H3.1: Linear alkanes
General molecular formula: CnH2n+2
Type of molecules: acyclic, saturated, hydrocarbon, linear or branched
Hybridisation & bounds C atoms: sp3-hybridised, 4 covalent bounds
Formal oxidation state of C atoms: -4 to 0
Isomerism
= Molecules with the same kinds and numbers of atoms (same molecular formula) joined up in different ways.
Isomers Constitutional isomers
Stereoisomers Conformational isomers
Configurational isomers Enantiomers
Diastereomers
Explanation of concepts:
Concept Explanation Example
Constitutional isomers Same molecular formula but different connectivity
Stereoisomers Same molecular formula and connectivity, but
different spatial arrangement of atoms
Conformational isomers Can be interconverted by rotation around a bond -Staggered, eclipsed, …
(only σ-bond) -Chair conformations
Configurational isomers Can’t be interconverted by rotation around a bond -(E) and (Z) (around π-bond)
-Cis and trans decalin
-Chiral centres
Enantiomers Image and mirror image -Chiral centres
Diastereomers Not mirror images of each other. This occurs in -(E) and (Z) (around π-bond)
molecules with 2 or more stereo centres, where -Cis and trans decalin
the configuration is different at some but not all of -Multiple chiral centres, not
them. mirror images of each other
Constitutional isomers of alkanes:
Propanes
Butanes
Pentanes
Hexanes
Constitutional isomerism
Different chemical & physical properties
- Boiling point: linear alkanes are higher than branched alkanes
- Linear alkanes are thermodynamically less stable than branched alkanes
3
